1. Field of the Invention
The present invention relates to a computer network, and more particularly, to a network-device management apparatus and method relating to a network-device management program for controlling network devices connected to a computer network.
2. Description of the Related Art
Today, computers are often interconnected via a local area network (LAN). The local area network is constructed in a floor or the entirety of a building, a group of buildings (an enclosure), a local area, or a larger area. It is also possible to interconnect such networks, and connect the networks to a worldwide network. Each of such interconnected LANs has, in some cases, various hardware interconnecting techniques and a plurality of network protocols.
In a simple LAN isolated from other LANs, each user can exchange an apparatus, install software, or examine problems.
On the other hand, in a large-scale complicated LAN or a large group of interconnected LANs, “management” is required. The word “management” indicates management by both a network device manager (a human being), and software used by that manager.
In the present invention, the word “management” indicates management by software (a network-device management program) for managing the entire system, and the word “user” indicates a human being who uses the network-device management program. Usually, the user is a network-device manager or a person responsible for system management. By using a network-device management program, the user can obtain management data from each network device and change the management data.
Usually, a large-scale network system is a dynamic system in which addition or removal of an apparatus, updating of software, detection of problems, and the like are incessantly performed. A description will now be provided of a large-scale network which requires “management”.
FIG. 1 is a diagram illustrating a large-scale network. Usually, a printer 102 having an open architecture is connected to a network via a network board (NB) 101. The NB 101 is connected to a LAN 100 via a LAN interface, such as an Ethernet interface 10Base-2 having a coaxial connector, or 10Base-T having RJ-45, or the like.
A plurality of personal computers (PCs), such as a PC 103, a PC 104 and the like, are also connected to the LAN 100. These PC 103, PC 204 and the like can communicate with the NB 101 under the control of a network operating device. The user can use the PC103 as a PC for managing network devices. A local printer 105 is connected to the PC104. Similarly, a local printer, such as the printer 105 or the like, may be connected to the PC103, although such is not shown in FIG. 1.
A file server 106 is also connected to the LAN 100. The file server 106 manages access to a file stored in a large-capacity (for example, ten billion bytes) network disk 107. A print server 108 manages printing requests to a plurality of printers 109, the printer 105 installed at a remote location, and the like. Any other peripheral apparatus (not shown) may also be connected to the LAN 100.
A WWW (world wide web) server 150 is also connected to the LAN 100. The WWW server 150 transmits an HTML (Hyper Text Markup Language) document generated by an installed network-device management program to the PC 103, which can display the HTML document on a display by means of an installed WWW browser. Alternatively, when the user performs setting of a printer using the WWW browser in the PC 103, the PC 103 can transmit the contents of the setting to a specific printer via the network-device management program of the WWW server 150.
More specifically, in the network shown in FIG. 1, in order to perform efficient communication between various network members, network software, such as Novell®, NetWare®, UNIX® or the like, may be used. Although any network software may be used, NetWare (a registered trademark of the Novell Corporation; hereinafter omitted) software is an example of software that is fully suited for this use. For more detailed description relating to this software package, refer to the on-line documentation enclosed in the NetWare package). This documentation can be purchased from the Novell Corporation together with the NetWare package.
FIG. 1 will now be briefly described. The file server 106 operates as a file management unit, and performs reception, storage, queuing, caching, and transmission of files. For example, data files formed by each of the PC 103 and PC 104 are transmitted to the file server 106. The file server 106 sequentially arranges these data files and performs queuing, and sequentially transmits the data files to a printer 109 in accordance with a command from the print server 108.
Each of the PC 103 and PC 104 is an ordinary PC which can perform generation of a data file, transmission of the generated data file to the LAN 100, reception of files from the LAN 100, and display and/or processing of the received files.
Although only PCs are illustrated in FIG. 1, any other computers which are suitable for executing network software may also be connected to the network. For example, when UNIX software is used, UNIX workstations may be connected to the network. Such workstations may be used together with the illustrated PCs in an appropriate situation.
Usually, the LAN provides a relatively local user group, for example, a user group on a single floor or on a plurality of consecutive floors within a building with service. As the distance between users increases, for example, when users are located in different buildings or prefectures, a wide-area network (WAN) may be constructed. A WAN is basically an aggregate of LANs formed by interconnecting various LANs with a high-speed digital network, such as ISDN (Integrated Services Digital Network) or the like. Accordingly, as shown in FIG. 1, a WAN is formed by interconnecting the LAN 100, a LAN 110 and a LAN 120 via modem/transponders 130, 130b and a backbone 140.
Dedicated PCs, and if necessary, a file server and a print server, are connected to each of the LANs. As shown in FIG. 1, a PC 111, a PC 112, a file server 113, a network disk 114, a print server 115 and a number of printers 116 are connected to the LAN 110. On the other hand, only a PC 121 and a PC 122 are connected to the LAN 120. The devices connected to the LAN 100, the LAN 110 and the LAN 120 can access the functions of apparatuses connected to other LANs via the WAN connection.
In order to manage devices connected to networks constituting such a large-scale network system, various attempts have been made by a large number of standardization organizations. The International Organization for Standardization (ISO) has provided a general-purpose standard framework called an Open System Interconnection (OSI) model. The OSI model of a network-device control protocol is called a Common Management Information Protocol (CMIP). The CMIP is a network-device control protocol common in Europe.
Recently, a modification of the CMIP, called a Simple Network Management Protocol (SNMP), has been used as a network-device management protocol capable of being more commonly used (see the first edition, Aug. 20, 1992, of “Introduction to TCP/IP Network-Device Management: Aiming at Practical Management” written by M. T. Rose, translated by Takeshi Nishida, published by Toppan Printing Company, Limited).
A network-device management system according to this SNMP network-device management technique includes at least one network-device management station (NMS), a plurality of nodes to be managed, each including an agent, and a network-device management protocol to be used by the network-device management station and the agent for exchanging management information. Usually, the user can obtain data on the network or change the data by communicating with agent software on a node to be managed using a network-device management program in the NMS.
The word “agent” indicates software running at each node to be managed as a background process. When the user requests management data to a device on the network, the network-device management program puts object identifying information in a management packet or frame, and transmits the packet or frame to the agent of the device. The agent interprets the object identifying information, puts data corresponding to the object identifying information in a packet, and transmits the packet to the network-device management program. The agent calls, in some cases, a corresponding process in order to extract data.
The agent holds management data relating to the state of the device in the form of a database. This database is called an MIB (management information base). The MIB has the data structure of a tree, in which all nodes are uniquely numbered. An identifier for each of the nodes is called an object identifier.
The structure of the MIB is called a Structure of Management Information (SMI), which is provided in “RFC1155 Structure and Identification of Management Information for TCP/IP-Based Internets”.
In this specification, management data for a network device is equivalent to information allocated to the MIB object identifier (MIB information).
Next, the SNMP will be briefly described. Communication is performed between a PC (manager) where the network-device management program operates and a network device (agent) to be managed where an SNMP agent operates using the SNMP. The SNMP has five types of commands, i.e., Get-request, Get-next-request, Get-response, Set-request, and Trap.
Get-request and Get-next-request commands are commands to be transmitted from the manager to the agent in order for the manager to acquire the value of the MIB object (MIB information) of the agent. The agent which has received this command transmits a Get-response command in order to notify the manager of the value of the MIB object.
A Set-request command is a command transmitted from the manager to the agent in order for the manager to set the value of the MIB object of the agent. The agent which has received this command sets the value of the MIB object, and transmits a Get-response command to the manager in order to notify the manager of the result of the setting.
A Trap command is a command transmitted from the agent to the manager in order to notify the manager of a change in the state of the agent's own device.
A system is well known in which the SNMP agent operates in the printer itself or the network board (NB 101) connected to the printer, and the network-device management program, serving as the SNMP manager, operates in the PC.